It often has become desirable to plant seeds at varying levels beneath the ground surface due to the inability to predict weather during germination and early growth stages. Seeds planted deeply, in certain weather conditions, will fail to reach the ground surface. Likewise, as a result of weather conditions, seeds planted close to the ground surface can be adversely affected by cold or extremely rainy weather in which early germinating seeds are killed by frost or, in some instances, even washed away.
Conventional seed drills include adjustments that facilitate selective planting depths. However, a substantial amount of time is involved in setting the individual seed planting "boots" of conventional seed drills at the selected soil depth. Furthermore, once the depth is set all the seed is planted at the same depth. Therefore, seeds planted too deep and affected by adverse weather conditions, will fail to grow. The affected area must then be re-seeded at a shallower depth or the entire affected area will pass through the growing and harvest season without producing.
It is desirable to obtain some form of attachment that will mount to existing seed drills to afford the capability of separating seed flow from a hopper and planting the seed with a selected percentage of seed at one level and the remainder at another level, thereby assuring germination and growth of seeds planted at least at one of the planting levels.
Apparatus have been developed for delivering seeds at different bedding levels from the same drill. Some designs receive seeds from individual hoppers, with each hopper delivering to its own delivery tube.
An exception to the above multi-hopper planting arrangement is disclosed in U.S. Pat. No. 1,362,834 to H. B. Barfield. Barfield discloses a cotton planter in which a single hopper delivers to a bifurcated seed delivery tube. At the vertex of the tube bifurcations is a flap that can be pivoted to cover one or the other seed tubes. Mechanism is attached to the flap to alternately operate it to shift one direction or the other to alternately drop seeds through the bifurcated tubes. One hundred percent seed flow is thus alternated between the bifurcated tubes, leaving a succession of unplanted spaces between groups of planted seeds.
U.S. Pat. No. 1,229,604 is exemplary of a planter in which two individual hoppers are used with associated delivery tubes for directing seed, or a combination of seed and fertilizer at selected levels. Other efforts have resulted in planters in which single hoppers deliver to a pair of seed delivery tubes rather than a single tube. By providing a pair of tubes leading from a single hopper, the user is able to selectively plant at two or more depths. This arrangement may very well be serviceable but requires the purchase of a drill having such capabilities.
Patents disclosing examples of multiple seed delivery tubes extending from single hoppers are: U.S. Pat. Nos. 1,075,668; 993,183; 904,410; 872,363; 1,591,793; 1,291,164; and 3,398,707.